Abstract

The ratio of prompt negative muons to negative pions produced in the forward direction by the interaction of 400-GeV protons on copper has been determined to be 5.8 × 10−5 for 55-GeV muons, 3.05 × 10−5 for 102-GeV muons, and 1.93 × 10−5 for 230-GeV muons. The ratio of prompt positive muons to negative muons was about 1.